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A server is a program, which waits for the establishment of contact of a Client program and exchanges after establishment of contact with this message.
Remarks
Communication takes place thereby after the Client server system. In the information technology an alternative to the Client server principle is the Peer ton Peer principle.
One calls the rules, which determine the format as well as the meaning of the messages exchanged between servers and Client, minutes.
One calls the hardware, on which one or more servers run, host.
The term server is colloquially also often used, in order to designate computers in a computer network, on which an application of servers is implemented.
Availability and Clustering
A server runs either permanently (daemon mode) or on request of a Clients is started (see inetd). In order to increase the reliability and efficiency, several servers can be hooked up as cluster. These can be distributed both on one and on several host. Breaks in or if several servers fail, then the still existing servers take over the inquiry of the Clients.
Examples
- Servers, which implement HTTP minutes, are called HTTP servers. An access is made by HTTP Clients. HTTP is used particularly by the World Wide Web (WWW). HTTPS is a variant of HTTP, with which log data will coded transfer.
- Servers, which implement minutes for file transmission, are generally called file, data or file servers. The most frequently used file transmission protocols are ftp, SFTP, NFS and SMB/CIFS.
Further examples
- By means of print servers (printer servers) users receive access to distant printers.
- By means of time servers (time server, network Time Protocolserver) computer clocks are synchronized.
- Mailserver (E-Mail server) and new servers serve communication.
- Root servers are the most important name servers of the Domain Name of system.
- Baking UP servers, which administer the archiving of the volume of data.
- On play servers (Gameservern) several players can play together or against each other.
- With a Streaming server one can radiate for example Internet radio.
- Data base servers administer one or more data base systems.
- emulated server systems are more vServer. Run several more vServer on a server.
- Web servers are server services, which make HTTP minutes available on a computer.
- A pro XY server puts information other computers to buffered at the disposal.
- A terminal server puts an emulated working environment to other computers (usually Thin Clients) at the disposal.
- A DHCP server assigns among other things dynamically IP addresses to computers in the network.
- An IRC server mediate the data under Chatteilnehmern.
- A file transfer service makes the transmission of files possible between computers. Most well-known and usually-used TCP/IP minutes at all are ftp.
- A file access service and/or a Network File System permits a working on of distant files over a Client. Generally also competitive accesses are possible. Contrary to a file transfer service not the entire files, but only the operations applied to the files and the pertinent data will transfer. Well-known services are for example NFS, SMB.
Literature
- Douglas E. Comer: Computer networks and Internets. Pearson study, ISBN 3-8273-7023-X
- Craig Hunt: TCP/IP. O' Reilly, ISBN 3-89721-179-3
- Hans's Robert Hansen, Gustaf Neumann: Work book economical informatics. 6. Aufl. UTB, Stuttgart 2002, ISBN 3825212815